Tricky one because of its shape - what are the base dimensions? Whats your water like in terms of hardness too?
The tough bit will be that you likely need to stick to nano or pico species so hopefully if you have softwater you could still do something cool. A trio of Tiger Badis would be cool, with some chilli rasbora, cherry shrimp and if soft enough clown killifish? Or if you have harder water go for Endlers and Emerald Rasboras with some shrimp and snails - cherry could be ok still or go for Amanos.
Wills